Tent liner: You see these a lot in bridal magazines. It’s a floaty, parachute-looking lining, usually white or ivory, though you can get insane colors for insane prices. Even in your basic white, these can get pretty expensive, usually 1x-4x the cost of the tent itself. Bridal magazines try to make these sound as essential as a best man and a marriage license, but fortunately, like sterling silver flatware, this is a fancy detail 98% of people can skip. Instead of a liner, get a pole tent. Check out the picture: the peak is made via one single pole instead of lots of interior frames and what-not, so you don’t even need a liner. And if you do get a liner, don’t blow a ton of money on a custom fuchsia-colored one with your name all over it, when you can use lighting effects on a normal liner to get a similar look.
Walls: $1-3 per linear foot (the perimeter of the tent). The perimeter of our imaginary 40×80 tent is 40+40+80+80, so you’d need 240 foot of wall. Solids, clear, and cathedral are standard. Fabric walls are nice, but they are strictly for decoration–they will not keep you dry.
Whether or not you need walls depends on time of year. The dead of summer? This is North Carolina. Skip the walls–they’ll just make your tent hot, and add fans instead. The winter? Get walls and heat. Some people try to use patio heaters inside tents, but don’t do that–get an actual tent furnace. These have a thermostat built in, just like the heat in your house, so you don’t have to keep adjusting it during your event, and 90% of it sits outside the tent so it doesn’t take up space. Plus you don’t have to worry about somebody knocking it over.